Exercise is an effective strategy to prevent and improve obesity and related metabolic diseases. Exercise increases the metabolic demand in the body. Although many of the metabolic health benefits of exercise depend on skeletal muscle adaptations, exercise exerts many of its metabolic effects through the liver, adipose tissue, and pancreas. Therefore, exercise is the physiological state in which inter-organ signaling is most important. By contrast, circadian rhythms in mammals are associated with the regulation of several physiological and biological functions, including body temperature, sleep-wake cycle, physical activity, hormone secretion, and metabolism, which are controlled by clock genes. Glucose and lipid tolerance reportedly exhibit diurnal variations, being lower in the evening than in the morning. Therefore, the effects of exercise on substrate metabolism at different times of the day may differ. In this review, the importance of exercise timing considerations will be outlined, incorporating a chrono-exercise perspective.

This study aimed to investigate the acute change of static stretching (SS) on autonomic nerve activity and to clarify the effect of SS on systemic circulation. Twenty healthy young, male volunteers performed a 1-min SS motion of the right triceps surae muscle, repeated five times. The autonomic nerve activity balance was obtained using second derivatives of the photoplethysmogram readings before (pre), during, and after (post) SS. Heart rate and blood pressure (BP) were also measured. The autonomic nerve activity significantly changed to parasympathetic dominance by SS as compared with pre. In addition, for SS, the autonomic nerve activity slowly changed to sympathetic dominance after completion of all sets of stretching, but these value did not return to pre during the 5 minutes after the completion of all sets of stretching, with parasympathetic dominance continuing by 4 minutes after SS. The BP and HR transiently increased during SS and decreased after SS. In addition, HR significantly decreased after completion of all sets of SS.The possibility that the response during SS may differ from the response during active static stretching is shown.

A noninvasive, immediate, and convenient method for assessing muscle tissue status during exercise-induced muscle damage (EIMD) has not been established. This study was designed to assess and determine parameters suitable for measuring EIMD after eccentric exercise, using multi-frequency bioimpedance analysis (BIA). Thirty-five young male participants performed dumbbell exercises with their left arm, and their BIA parameters were measured at various time points up to 168 h post exercise using a multi-frequency BIA device. At all-time points, intra and extracellular water content was greater in the left arm than in the right arm, whereas the impedance, reactance, resistance, and phase angle were lower in the left arm than in the right arm. Established EIMD indices, such as maximal isometric voluntary contraction, were measured and used in correlational analyses. Only reactance was correlated with biomarkers, indicating muscle damage (r = − 0.56 to − 0.49). Furthermore, reactance was found to correlate well with indirect indicators of EIMD, suggesting that it may be a suitable marker for evaluating EIMD. However, the relationship with the limited evaluation indices employed in this study is constrained. Future studies should investigate the correlation between reactance and direct damage indicators, such as structural damage, observed in biopsies.